I can't seem to find one, so here we go! I'm far from an expert, but I thought I'd post some starters and go from there. Related genres would probably be things like trip-hop, acid jazz (I'll pretend I know what that is exactly), and some of the hip-hoppish stuff that tends not to be focused on vocals as much. IDM has it's own thread so I'll try to leave that out. Here's some sounds (I'll skip the few ones everyone knows about, like Portishead, DJ Shadow or Massive Attack):

I saw Bonobo live in May and the show was loving killer. Going to see him again in November and I can't wait.

Here's another favorite of mine: Vibrasphere. They broke up a few years ago, but they've been one of my favorite electronic acts since I first heard their stuff in 2007 when their album Exploring The Tributaries came out. Most of what they made was either downtempo stuff or psytrance, so different sides of the spectrum. While I enjoyed everything they made, their downtempo stuff was my favorite. Here's some of my favorite tracks of theirs: